Different influences of u-InGaN upper waveguide on the performance of GaN-based blue and green laser diodes

Performances of blue and green laser diodes (LDs) with different u-InGaN upper waveguides (UWGs) are investigated theoretically by using LASTIP. It is found that the slope efficiency (SE) of blue LD decreases due to great optical loss when the indium content of u-InGaN UWG is more than 0.02, although its leakage current decreases obviously. Meanwhile the SE of the green LD increases when the indium content of u-InGaN UWG is varied from 0 to 0.05, which is attributed to the reduction of leakage current and the small increase of optical loss. Therefore, a new blue LD structure with In_0.05Ga_0.95N lower waveguide (LWG) is designed to reduce the optical loss, and its slope efficiency is improved significantly.